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Radar checks buildings after earthquakes
25 April 2011
Recent advances in ground-penetrating radar, GPR, could be used to help structural engineers and conservationists assess the stability of historic buildings or buildings affected by earthquakes that otherwise appear sound.
Writing in the International Journal of Materials and Structural Integrity, researchers in Italy explain how higher frequency antennae, bipolar antennae, positioning systems and 3D software work together to extend the potential of GPR for diagnostic applications to masonry structures. Luigia Binda and colleagues in the Department of Structural Engineering, at the Polytechnic of Milan, point out that preservation and rehabilitation of historic and other buildings can only be accomplished successfully if a careful diagnosis of the state of any structural damage has been carried out.
GPR is commonly used for geological surveys and scientific research allowing voids and cracks to be detected in rock, soil and ice. Previous researchers had suggested that it could be used to assess a building's structural integrity. However, until now the technology has not been adequate for the more detailed needs of such work. The authors have now tested modern GPR in assessing numerous buildings across Italy and have demonstrated that it is possible to locate the position of large voids and inclusions of different materials, like steel and wood, to qualify the state of conservation or damage of the walls and to define the presence and the level of moisture. GPR can also now reveal the morphology of wall sections in multiply layered stone and brick masonry structures and to detect hidden cracks or discontinuities in walls. Critically, it can also verify the effectiveness of repairs.
The team concedes that much work remains to be done in developing GPR for assessing historic and earthquake-damaged buildings. However, in combination with various other techniques, including optical boroscopy, flat-jack, sonic tests, and thermography it can provide a much-needed and far clearer picture of building stability than was previously possible.